Just an additional comment for all those still waiting for this bug to
be fixed: current version of Handcent saves the "sent time" of the
messages. It can be seen on "message details". It's not the perfect
solution but it's the best solution that we have right now.

"SMS
Timestamper Fix" from andrperk worked for me most of the times but not
always.

Additionally, some commenters have reported that certain handsets do not suffer from this bug, presumably because the manufacturer patched it themselves in their messaging application or SMS framework.